1. Field of the Invention
The present invention relates to a disk cartridge in which a disc-shaped disk medium used as a medium to/from which information and a video image is recorded/reproduced is rotatably housed in a case.
2. Description of the Related Art
As a recording/reproducing medium for a portable computer and a recording/reproducing medium of a video image, for example, disc-shaped disk media such as an optical disk and a magnet optical disk are used. At the time of recording or reproduction, while being rotated by a spindle shaft in a state where such a disk medium is loaded on a disk drive device, a recording layer of the disk medium is irradiated with a laser beam or both a laser beam and a magnetic field by a recording head accessing a recording face side of the disk medium. With the configuration, in the disk medium, information is recorded by decomposition of the recording layer and/or formation of a pit, a phase change, a magnetization inversion or the like by a temperature rise, or recorded information is reproduced with a reproducing head by reading variations in the reflectance of a laser beam or a polarization angle.
There is a known disk cartridge in which a disk medium is housed in a housing part of a case in order to prevent adhesion of dusts and the like onto the recording layer in the disk medium as the recording capacity of the disk medium increases (refer to, for example, Japanese Patent Application Laid-Open (JP-A) No. 2003-115184). In such a disk cartridge, a chucking opening and a head opening for accessing a center hole in the disk medium and the recording layer side are formed on the recording layer side of the disk medium in the case. The openings are closed by a pair of shutters driven by an inner rotor.
There is another known disk cartridge having an opening through which a disk medium can be inserted/ejected on the side opposite to the chucking opening and the head opening for the disk medium in the case (for example, refer to JP-A No. 2003-242740). In the disk cartridge, the openings are provided and a pair of shutters and also the inner rotor is operated in the same plane, thereby reducing the thickness. The shutter mechanism of the disk cartridge will be described with reference to FIGS. 18A and 18B.
A disk cartridge 100 shown in FIGS. 18A and 18B has, in a bottom plate 102A of a case 102, a chucking opening 104 for accessing the center hole in a disk medium (not shown in figure) and a head opening 106 through which the head of a drive device accesses a recording face. Between a disk medium in the case 102 and the bottom plate 102A, a first shutter 108 turnable coaxially with the disk medium and a second shutter 110 having a swing shaft 112 on the outside in the radial direction of the disk medium in the case 102 are provided.
A contact end face 108A of the first shutter 108 and a contact end face 110A of the second shutter 110, as ends which come into contact with each other as shown in FIG. 18A are allowed to come into contact with each other to close the head opening 106, and the chucking opening 104 is always maintained in an open state. By turning the first shutter 108 in the direction of the arrow G and turning the second shutter 110 in the direction of the arrow H which is almost opposite to the arrow G with respect to the head opening 106, as shown in FIG. 18B, the head opening 106 is opened.
The contact end faces 108A and 110A of the first shutter 108 and the second shutter 110 have straight lines. In the disk cartridge 100, the contact end face 110A is moved apart from/close to the contact end face 108A while drawing a locus of relative movement at an acute angle with respect to the contact end face 108A. Consequently, when the angle θ formed between a straight line L4 (refer to FIG. 18A) connecting the axis of the swing shaft 112 of the second shutter 110 and an end Z at the head side in the closing direction in the contact end face 110A and the contact end face 110A is an acute angle, in a state where the head opening 106 is closed, the second shutter 110 cannot move in the direction of the arrow H until the first shutter 108 is turned in the direction of the arrow G more than a predetermined distance.
In the configuration disclosed in JP-A No. 2003-242740, the angle θ is set as an obtuse angle. Consequently, in a state where the head opening 106 is open as shown in FIG. 18B, the contact end face 108A of the first shutter 108 is inclined in the direction of opening wider from an edge 106A of the head opening 106 so as to be in a position further turned to the arrow G side more than the right-side edge 106A which is parallel to a loading direction A to the drive device of the head opening 106. In other words, a notch in the first shutter 108 is formed larger than the head opening 106, and the second shutter 110 becomes larger by the amount of enlarging the notch of the first shutter 108. Therefore, in the conventional disk cartridge 100, there is a case such that the second shutter 110 cannot be housed in the limited space in the case 102 in a state where the head opening 106 is open, that is, the head opening 106 having a predetermined size cannot be completely opened due to dimensional errors and assembly errors of the parts.
In the disk cartridge 100, the head opening 106 is closed by making the contact end faces 108A and 110A extending in the plate thickness direction of the first and second shutters 108 and 110 come into contact with each other. Consequently, there is the possibility that a gap is generated between the contact end faces 108A and 110A in a state where the head opening 106 is closed due to the dimensional errors and assembly errors of the first shutter 108 or second shutter 110. The gap causes invasion of dusts into the case 102, specifically, adhesion of dusts onto the recording face of a disk medium.
JP-A No. 2003-242740 discloses that the contact end faces 108A and 110A can be also formed as inclined faces, which match each other. With the configuration, even if a gap is created between the contact end faces 108A and 110A, invasion of dusts into the case 102 is suppressed. However, even with the configuration, a gap having a linear shape in cross sectional view along the inclined faces of the contact end faces 108A and 110A is created, so that the technique is not sufficient as a countermeasure against dusts.
On the other hand, Japanese Patent Laid-open No. 2003-115184 discloses a configuration that the end faces of a pair of shutters disposed between an inner rotor and the bottom plate of a case are in contact with each other and the pair of shutters overlap each other in the vertical direction. However, when the overlap structure is intended to be applied to the disk cartridge 100, the size of the second shutter 110 further increases, and it becomes difficult to completely open the head opening 106 having a required size. On the other hand, when a visor portion is extended from the contact end face 108A of the first shutter 108, the visor portion extends into the head opening in a state where the head opening 106 is open and, as a result, the head opening 106 cannot be perfectly opened. In addition, the head opening cannot be enlarged to permit an access of a large recording/reproduction head.
Further, a disk cartridge having another shutter mechanism for operating a pair of shutters in the same plane is also known (refer to, for example, JP-A No. 2002-269944). Although not shown in figure, in the configuration, the axis of turn of the second shutter is positioned on the right side whereas the swing shaft 112 of the second shutter of the above-described disk cartridge 100 is positioned on the left side of the drawing sheet, which is opposite to the above. Therefore, the contact end face of the second shutter is moved apart from/close to the contact end face of the first shutter while drawing the locus of relative movement at an obtuse angle. Consequently, in the conventional configuration, the operation of the second shutter does not interfere with the first shutter. In the configuration, however, the closed portion of the head opening by the second shutter and the axis of turn are far from each other, so that the second shutter becomes large (long). In addition, a cam mechanism for making the first and second shutters operate interlockingly has to be disposed near the axis of turn of the first shutter. A large force is necessary to open/close the head opening, and it is difficult to smoothly operate the first and second shutters.